2O 



slab of 4-in. to 6-in. to be supported on the decking. 

 There are so many conditions that it is impossible to 

 give any hard and fast rules about putting in joists. 

 It is a matter of judgment and experience. The joists 

 must not be spaced too far apart or the decking will 

 spring, and the joists themselves will deflect unduly. 

 On the other hand with big spans, which mean long 

 joists, it is often expedient to put a stringer, 4x4 say, 

 under the centers of the joists and shore it up to take 

 the strain off the joists. This will save spacing the 

 joists too close together and prevent too great a load 

 being carried to the beam sides and shores. As a rule 

 the joists are placed without any nailing whatever; at 

 any rate none at the bottom. In wrecking the floor, 

 knock in the bottom, till the joist falls over, when it 

 can be taken down at once and out of the way. This 

 may not be practicable with 2x4 joists. These might 

 well be mounted on little wedges resting on the ledger 

 board, which could be loosened to knock the joists out 

 again. 



Lastly the sheeting or decking. Like joists, the 

 question of kind of lumber is determined by judgment 

 and experience. In fact that is true of all centering. 

 Probably i-in. stuff surfaced is used oftener than any 

 other. If you have to present a first class ceiling sur- 

 face use matched or ship-lapped lumber. No mortar 

 ran run out of the mass of concrete to leave unsightly 

 crevasses with the aggregate showing. 



As mentioned before, if the floors are typical and the 

 -luvlitii; is to be used over and over, it is common to 

 form the sheeting in a solid panel or in half panels of 

 moderate size. The strips are simply fastened together 

 by nailing cleats underneath just sufficient to hold all, 

 with moderate usage, true and accurate to line. 



We said under beam and girder sides that they 

 should extend to the under side of the slab. This 

 means that the sheeting would be fitted up flush against 

 that part of the beam forms and would serve to brace 



